[多项选择]全世界人口数字的变化编写起来要难办得多，因为许多不发达国家并不保持完整的记录。然而，《联合国人口年鉴》每年都公布一份可收集到的人口统计数字详表。人口学家们根据对这些数字的认真研究，对一个现代工业国家人口史上所发生的情形作出自己的描述。他们认为，就历史上大部分时期而论，人类总的说是死亡率高、出生率也高。死亡率高的原因可能在于杀婴、疫病流行或饥荒，而这种情况是传统的部落和农民社会所特有的。因为有大量婴儿出生与之保持平衡，人口的规模总是保持稳定。

参考答案:
World figures for population changes are much more difficult to compile because many underdeveloped countries do not keep complete records. However, a very detailed list of the available statistics is published every year in the United Nations Demographic Yearbook. From a careful study of these figures, demographers have worked out a description of what they think happened in the history of the population of a modern industrial nation. Throughout most of human history, they believe, man has had a very high death-rate and a high birth-rate. The death-rate may have been due to infanticide, epidemic diseases or starvation, but it was typical of traditional tribal and peasant societies. Since it was balanced by large numbers of births, the size of the population remained stable.